With the immigration debate about to ramp up again this week, lawmakers are awash in data from advocates on both sides. The central debate will be about the best, most efficient, most secure way to bring undocumented immigrants into the light. But equally as important for the future engine of economic growth is the debate over visas for foreign students and incentives to get them to stay in the U.S. Weirdly, until very recently, those outside the government didn't have a full picture of those who've come here to study. A FOIA request by a Brookings researcher has turned up some very interesting results.

In 2010, nearly 700,000 foreign students studied here — that's about 21 percent of all those who took their college-level instruction outside their home countries.

A full 61 percent come from Asia, with a plurality — 25 percent — coming from China, followed by India (13 percent) and South Korea (9 percent).

Not surprisingly, most students apply for schools in cosmopolitan coastal cities like New York, Los Angeles, and San Francisco. Still, middle America has a much higher percentage of foreign students relative to their native-born students, particularly the big state universities.

How hard is it, under the current visa system, to retain the students who do science, math, and engineering work? About 1 out of every 5 gets sponsored for an H-1B visa, which allows them to stay and work for six years. Generally, one out of every seven F-1 visa students is sponsored and accepted for an H-1B.

And now you know why corporations would love to expand this system. And you also see the policy conundrum: Foreign students who can stay and take high-paying tech/engineering and science jobs crowd out American students applying for the same positions. Of course, the supply of students with degrees and expertise creates its own demand.